Stock-Based Awards

12 Months Ended

Dec. 31, 2025

Share-Based Payment Arrangement [Abstract]

Equity Incentive Plans

The Company's equity incentive plans, the 2017 Equity Incentive Plan (the “2017 Plan”), and previously, the 2015 Stock Incentive Plan (the “2015 Plan”), reserve shares of common stock for the issuance of stock options, restricted stock and other stock awards, to employees, non-employee directors, and consultants under terms and provisions established by the board of directors and approved by the stockholders. Upon adoption of the 2017 Plan, no new awards or grants are permitted under the 2015 Plan. The 2015 Plan continues to govern restricted stock awards and option awards previously granted thereunder.

Awards granted under the 2017 Plan and 2015 Plan expire no later than ten years from the date of grant. For stock options, the option price shall not be less than 100% of the estimated fair value of the Company's common stock on the day of grant. Options granted typically vest over a four-year period but may be granted with different vesting terms.

The 2017 Plan provides that the number of shares reserved and available for issuance under the 2017 Plan will automatically increase each January 1, beginning on January 1, 2019, by the lesser of (i) 10.0 million shares, (ii) 5% of the outstanding shares on the last day of the immediately preceding fiscal year, or (iii) such number of shares determined by the administrator of the 2017 Plan. In 2025, common stock available for issuance under the 2017 Plan was increased by approximately 7.2 million shares as a result of this automatic increase provision. As of December 31, 2025 and 2024, there were approximately 14.8 million and 14.3 million common shares available for the Company to grant under the 2017 Plan, respectively.

Stock Option Activity

The following table summarizes option award activity under the 2017 Plan and the 2015 Plan:


	Number of Options	Weighted- Average Exercise Price		Weighted- Average remaining contractual life (years)	Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2024	18,660,150	$	25.99	5.94	$	48,266
Granted	5,019,276	19.57
Exercised	(773,881)	1.81
Forfeited	(734,841)	25.16
Expired	(844,371)	0.68
Balance at December 31, 2025	21,326,333	$	26.39	6.21	$	10,658
Vested and expected to vest at December 31, 2025	21,326,333	$	26.39	6.21	$	10,658
Exercisable at December 31, 2025	13,674,635	$	29.46	4.84	$	8,497

Aggregate intrinsic value represents the difference between the fair value of the Company's common stock and the exercise price of outstanding options. The total intrinsic value of options exercised was $10.8 million, $10.6 million, and $12.1 million as of December 31, 2025, 2024 and 2023, respectively. During the years ended December 31, 2025, 2024, and 2023 the weighted-average grant-date fair value of the options vested was $16.30, $23.61, and $24.30 per share, respectively. The weighted-average grant date fair value of all options granted during the years ended December 31, 2025, 2024 and 2023 was $12.35, $12.99, and $17.95 per share, respectively.

Stock Options Granted to Employees with Service-Based Vesting

The estimated fair value of stock options granted to employees were calculated using the Black-Scholes option-pricing model, which requires various assumptions, including the fair value of the Company’s common stock, expected term, expected dividend yield, expected volatility, and the risk-free interest rate. The fair value of the Company’s common stock is based on the current market price, unless an adjustment is determined to be required, through discussion with senior management, due to material non-public information known by the Company at the time of grant. The expected volatility used in valuing stock options granted in 2024 and 2025 is based solely on the historical volatility of the Company’s common stock. For 2023, because the Company did not have sufficient trading history to rely exclusively on its own stock price volatility, expected volatility was determined using a combination of the Company’s historical volatility and the historical volatility of comparable publicly traded biotechnology and pharmaceutical companies over a period consistent with the expected term of the awards. Management considers whether the Company is in possession of material non-public information at the time of grants when making certain estimates, including volatility and the fair value of the Company's common stock. The expected term of stock options represents the period that the Company’s stock-options are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term). The risk-free interest rate is based on the implied yield currently available on U.S. treasury notes with terms approximately equal to the expected life of the option. The expected dividend rate is zero as the Company currently has no history or expectation of declaring cash dividends on the Company’s common stock.

The following assumptions were used in estimating the fair value of grants during the year ended:


	December 31,
	2025	2024	2023
Expected term (in years)	5.50 - 6.08	5.50 - 6.08	5.50 - 6.08
Volatility	64.8% - 68.7%	64.5% - 66.0%	67.6% - 69.6%
Risk-free interest rate	3.6% - 4.5%	3.7% - 4.5%	3.4% - 4.8%
Dividend yield	—	—	—

Restricted Stock Activity

We grant restricted stock units ("RSUs") under the 2017 Plan. The fair value of restricted stock underlying the RSUs is determined based on the closing market price of the Company's common stock on the date of grant.

Aggregated information regarding RSUs granted under the Plan for the year ended December 31, 2025 is summarized below:


	Number of Units	Weighted-Average Fair Value at Date of Grant per Share
Unvested at December 31, 2024	4,128,514	$	27.33
Granted	2,726,354	18.76
Vested and released	(1,449,761)	32.12
Forfeited	(280,478)	21.49
Unvested and expected to vest at December 31, 2025	5,124,629	$	21.74

The aggregate intrinsic value of RSUs is calculated as the closing price per share of the Company's common stock on the last trading day of the fiscal period, multiplied by outstanding RSUs as of December 31, 2025. The total intrinsic value of RSUs expected to vest was $84.6 million as of December 31, 2025. During the years ended December 31, 2024 and 2023 the weighted-average grant-date fair value of RSUs granted was $21.01 and $27.38, respectively. The total fair value of RSUs that vested during the years ended December 31, 2025, 2024, and 2023 was $27.1 million, $27.6 million, and $31.6 million, respectively.

Stock-Based Compensation Expense

The Company’s stock-based compensation expense was as follows (in thousands):


	Year Ended December 31,
	2025		2024		2023
Research and development	$	59,490	$	59,146	$	62,901
General and administrative	40,143		43,732		45,201
Total	$	99,633	$	102,878	$	108,102

As of December 31, 2025, total unamortized stock-based compensation expense was $161.0 million. The weighted-average period over which such stock-based compensation expense will be recognized is approximately 2.5 years.

There was no tax benefit realized related to awards vested or exercised during the years ended December 31, 2025, 2024 and 2023. There is no deferred tax benefit on total stock-based compensation expense for the years ended December 31, 2025, 2024 and 2023 since the company has recorded a full valuation allowance on all deferred tax assets.